Process for the manufacture of perfluoralkylsulphonyl fluorides

ABSTRACT

IN WHICH R1, R2, R3, R4, R5 and R6 independently of one another denote hydrogen or a C1-C6-alkyl group, in hydrofluoric acid.   Process for manufacturing perfluoralkylsulphonyl fluorides which consists in electrolyzing cyclic unsaturated sulphones of the formula

llnlted States Patent 72] Inventors Peter Voss Leverkusen-Wlesdorl';Hans Nlederprum, Monheim, both of Germany [2|] Appl. No. 17,303

[22] Filed Mar. 6, 1970 [45] Patented Nov. 30, 1971 [73] AssigneeFarbenfnbrlken Bayer Aktiengesellschalt Leverkusen, Germany [32]Priority Mar. 13, 1969 [33] Germany 541 PROCESS FOR THE MANUFACTURE orPERFLUORALKYLSULPHONYL rwomnes Primary Examiner-John H. Mack AssistantExaminer-D. R. Valentine Attorney-Plumley & Tyner ABSTRACT: Process formanufacturing perfluoralkylsulphonyl fluorides which consists inelectrolyzing cyclic unsaturated sulphones of the formula RI R3 in whichR,, R R R R and R independently of one another denote hydrogen or a c -calkyl group, in

PROCESS FOR THE MANUFACTURE OF PERFLUORALKYLSULPHONYL FLUORIDES PROCESSFOR THE MANUFACTURE OF PERFLUORALKYLSULPHONYL FLUORIDES The presentinvention relates to a process for the manufacture ofperfluoralkylsulphonyl fluorides; more particularly it concerns aprocess for the manufacture of perfluoralkylsulphonyl fluorides whereincyclic unsaturated sulphones of general formula Theperfluoralkylsulphonyl fluorides manufactured accordmg to the inventionpossess considerable technical importance for the manufacture ofsurface-active substances and especially of water-repellant andoil-repellant agents for finishing textfles and other n1 a terialsElectrochemical fluorination processes for the manufacture ofperfluoralkylsulphonyl fluorides are already known. Thus, for example,according to the British Pat. No. 758,467, saturated alkanesulphonicacid halides, and according to the British Pat. No. 1,099,240 (=U.S.Pat. No. 3,423,299), saturated cyclic sulphones, are subjected toelectrochemical fluorination in anhydrous hydrofluoric acid. The processaccording to the invention is distinguished from these two processes inthat it starts from significantly cheaper starting products-the additionproducts of SO to a,w-diolefines are employed directly-and that itconsumes less current, which follows from the equations below: C,H SOcl+l0HF+l9l-arad C,F SO,F-l Cl +9.5l-l,

+ IOHF 16 Farad C H SO F 8H;

Since it was known from the literature [compare M. Sander, W. Blochl,Chemie-lng.-Technik 37 (1965), page 8] that olefmic compounds and evenaromatic compounds tend to polymerize in anhydrous hydrofluoric acid andlead to resinification of the electrodes, it was surprising that theelectrochemical fluorination of the unsaturated cyclic sulphones to beused according to the invention, in anhydrous hydrofluoric acid, furnishperfluorosulphonyl fluorides in good yields even in highly concentratedsolutions, for example 20 percent strengthsolutions.

As unsaturated cyclic sulphones to be used in the process according tothe invention there may for example be quoted:

(2-sthylbutadlene S0,)

(Butadlene 80,)

. CH3 C3H7 S S 0, (Isoprene 50,) t2-propy i lfl ii QIL CsHu 0H s s 0 O2(Z-pentylbutadiene 80,) (Piperylene S0,)

iCoHnn CH! CH s P s O,

(Z-n-hexylbutadlene S0,) (La dlmetbylbutadlene S0,)

(2, 3-dimethylbutadiene 80,)

The sulphones to be used are in general easily soluble in anhydroushydrofluoric acid and yield conductive solutions; it is not necessary toadd a salt which confers conductivity.

The electrochemical cell is best manufactured from a noncorroding metalsuch as nickel, Monel metal, gold-plated metal or molybdenum. it canalso consist of graphite or be lined with fluorocarbon plastics.

The cathodes and anodes can be manufactured from nickel, Monel metal,carbon or silicon carbide.

An electrolysis cell of nickel equipped with a packet of nickel anodeand cathode plates spaced at 3 mm. has proved to be most suitable.Suitable operating conditions have proved to be a voltage of about 45-6v., a current density of about 0.5 a./dm. and a concentration ofunsaturated cyclic sulphones in the hydrofluoric acid of 5-20 percent byweight relative to the weight of the anhydrous hydrofluoric acid.

The process according to the invention is in general carried out at alow temperature, generally below l0 C., preferably An operating periodof several hours or days is generally required in order to increase theyield of the process according to the invention to a maximum.

EXAMPLE I The electrolysis cell holds 9.61 in the ready-to-operatecondition. The electrode packet consists of 31 nickel plates (16cathodes and 15 anodes) of which the effective anode surface amounts to10,460 cm. corresponding, at a load of 50 amp., to a current density of0.005 a./cm.

The cell was charged with 2,000 g. of butadienesulphone and about 81g.of anhydrous hydrofluoric acid. The average electrolysis temperature was0 C. Hydrofluoric acid and butadienesulphone were discontinuously addedas required during the electrolysis, which lasted 740 hours. Thestarting product dissolved very well in the hydrofluoric acid. Theaddition of an electrolyte was not necessary. The average currentstrength was 42.9 amp. The voltage fluctuated between 4.7 and 6 volts.In total, 6,500 g. of butadienesulphone were employed. 8,694 g. of areaction product were run off at the bottom of the cell and according toanalysis by gaschromatography consisted to the extent of 86.90 percentof perfluorobutanesulphonyl fluoride. The boiling point of the purifiedC,F,,SOF lay between 64-65 C. The yield of substance was 45.0 percent.The current yield was 33.7 percent.

EXAMPLEZ 5 2,000 g. of the crude Z-methylsulpholene prepared by heatingsulfur dioxide and peroxide free l,3-pentadiene in a molar ratio of2,94zl and in the presence of catalytic amounts of hydroquinone in asealed vessel to 95 C. for 3 hours, were electrolyzed in the 9.61 celldescribed in example 1. It was not necessary to add an electrolyte. Thetemperature of the electrolysis cell fluctuated between 2 and +3 C. Thetemperature of the condenser was 60 C. During the electrolysis whichlasted 35] hours a total of 5,825 g. of crude 2-methylsulpholene wasemployed. The voltage fluctuated between 4.7 and 5.8 v., the averagevoltage was 5.14 v., and the average current strength was 45.7 a. Atotal of 4,941 g. of product was run off at the bottom of the cell.

As expected, two isomeric forms of perfluoropen- 1 tanesulphonylfluoride were produced on electrochemical fluorination ofZ-methylsulpholene by splitting of the C-S bond:

89.1 percent of the crude product produced consisted of I perfluorinatedsulphonyl fluoride, corresponding to a yield of substance of 33.5percent and a current yield of 38.4 percent.

EXAMPLE 3 2,000 g. of 3-methylsulpholene were dissolved in 81 g. ofanhydrous hydrofluoric acid and electrolyzed without the addition of asalt to confer conductivity. After 6 days a further 695 g. of thestarting product were added. After 273 hours and an average currentstrength of 54.4 amp. the total yield was 3,320 g. During the experimentthe voltage increased, at constant current strength, from 4.6 to 5.9volts. The average electrolysis temperature was 2 C. The resulting crudeproduct consisted, to the extent of 64.9 percent of aperfluoralkylsulphonic acid fluoride isomer mixture:

' ric=c-oa,

According to the 'F nuclear resonance spectrum the isomeric compoundsare present in the molar ratio of 2: l. The yield of substance was 30.0percent. The current yield was 22.0 percent.

EXAMPLE 4 l,000 g. of 3,4-dimethylsulpholene were dissolved in 9 l g. ofanhydrous hydrofluoric acid and electrolyzed, without the addition of asalt to confer conductivity, at 2 C. In total, 2,820 g. of sulpholenewere added. The maximum sulpholene concentration was 10 percent. After532 electrolysis hours at an average voltage of 5.6 v. and an averagecurrent strength of 57.8 a., 3,320 g. of perfluorinated sulphonylfluoride were drawn off at the bottom of the cell. Gaschromatography andanalysis showed that 44.7 percent of the reaction product consisted ofperfluoralkylsulphonyl fluorides.

CHrC=(i7-CH; I

HC C H, 24 Farad R Q: I.

in which R,, R R R,, R and R,, independently of one another denotehydrogen or a C-C alkyl group, are electrolyzed in anhydroushydrofluoric acid.

t I! I. i i

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,623,963 Dated Nov. 30, 1971 Inventor(s) Peter Oss et al.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

COLUMN LINE ERROR l 40 "C H SO cl" should be C H SO Cll 52 colling"should be --cooling-- 2 45 "a./dm should be A/dm 2 57 "9.61" should be-9.6 l-- 2 61 "a./cm should be -A/cm 2 63 "81 should be -8 l 3 l "C FSOF" should be C F SO F 3 12 "9.61" should be -9.6 l

3 48 "81g." should be -8 1 4 3 "+HF" should be -+l2 HF- 4 l6 "91g"should be 9 1 4 22 "a." should be -A-- 4 56 "CC should be --C -C Signedand sealed this 1st day of August 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GUTTSCHALK Attesting Officer Commissionerof Patents 2M P0-105O H0-59l USCOMM-OC 50375-959 9 U 5 GOVERNMENTPRINTING OFFICE |9690366-33l

1. Process for the manufacture of perfluoralkylsulphonyl fluorides ofgeneral formula RFSO2F in which RF denotes a linear or branchedperfluorocarbon residue having at least four C atoms, by electrochemicalfluorination in anhydrous hydrofluoric acid, characterized in thatcyclic unsaturated sulphones of general formula in which R1, R2, R3, R4,R5 and R6 independently of one another denote hydrogen or a C- C6 alkylgroup, are electrolyzed in anhydrous hydrofluoric acid.